README.md

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Docker-compose

• Wordpress with docker-compose.yml
  • Prepare docker-compose.yml
  • Add mysql service
  • Add wordpress service
  • Run the stack

Docker Compose is a tool that helps orchestration of structures composed of multiple containers. When writing this article, version 3.8 of Compose file format is available running under Docker 19.03.0+ (this is important due to the different template formats and arguments accepted by service).

In order to verify your current tool version, please run the following bash command:

docker-compose --version

More about the topic: https://docs.docker.com/compose/compose-file/

Wordpress with docker-compose.yml

Using Docker Compose, we need to define a Template file as entry point of the service (docker-compose.yml file). This file will describe services, networks and volumes that our containers will define - the best news is that all those objects can be run with a single line of code, awesome!

First example will show how to organize a simple stack running Wordpress image together with MySQL database.

• Prepare docker-compose.yml
• Add mysql service
• Add wordpress service
• Run the stack

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Prepare docker-compose.yml

We need a root directory where will be placed our docker-compose file:

1. create a new docker_compose_wordpress folder
2. create blank docker-compose.yml file inside docker_compose_wordpress
3. add initial parameters

version: '3.8'
services:

• version : indicates Compose file format
• services : configuration applied to each container started for that service (each part of the service references image that will be created)

Progress:

• Prepare docker-compose.yml
• Add mysql service
• Add wordpress service
• Run the stack

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Add mysql service

Wordpress needs a data storage, lets add then our favourite MySQL database:

version: '3.8'
services:
+  mysql:
+    image: mysql:8.0

• mysql : image name for the service element
• image : image used to as main build

As explained in the previous chapter - Containers are sateless and do not have data persistence - once deleted, the data that is not stored under shared volume(s) will be lost.

version: '3.8'
services:
   mysql:
     image: mysql:8.0
+    volumes:
+      - db_data:/var/lib/mysql
+ volumes:
+  db_data: {}

• volumes : volume name/path, it can be also dynamically assigned from environment variable (placed in an .env file)
• db_data : named volume "db_data:/var/lib/mysql:rw" is used in service "mysql"

Additional information about data connection:

version: '3.8'
services:
   mysql:
     image: mysql:8.0
     volumes:
       - db_data:/var/lib/mysql
+    restart: always
+    environment:
+      MYSQL_ROOT_PASSWORD: root
+      MYSQL_DATABASE: wordpress
+      MYSQL_USER: user
+      MYSQL_PASSWORD: pass
volumes:
  db_data: {}

• restart : restarts the container if it stops
• environment : regular connection variables used in mysql image

Progress:

• Prepare docker-compose.yml
• Add mysql service
• Add wordpress service
• Run the stack

---

Add wordpress service

Second part of the docker-compose file will implement Wordpress service - most of the parameters are similar to previous example:

version: '3.8'
services:
   mysql:
     image: mysql:8.0
     volumes:
       - db_data:/var/lib/mysql
     restart: always
     environment:
       MYSQL_ROOT_PASSWORD: somewordpress
       MYSQL_DATABASE: wordpress
       MYSQL_USER: wordpress
       MYSQL_PASSWORD: wordpress
+  wordpress:
+    depends_on:
+      - mysql
+    image: wordpress:latest
+    ports:
+      - "8000:80"
+    restart: always
+    environment:
+      WORDPRESS_DB_HOST: mysql:3306
+      WORDPRESS_DB_USER: wordpress
+      WORDPRESS_DB_PASSWORD: wordpress
+      WORDPRESS_DB_NAME: wordpress
volumes:
  db_data: {}

• depends_on : express dependency between services and mounting order (att: order does not mean that service will wait to start when another service finishes. We will see some trick to avoid potential side effects later in this chapter.)
• ports : ports mapping : (makes our sire reachable from http://127.0.0.1:8000/)

Source: docker-compose.yml

Progress:

• Prepare docker-compose.yml
• Add mysql service
• Add wordpress service
• Run the stack

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Run the stack

Our file is ready now, lets run the magic command:

docker-compose up -d

All the services should be now mounted, and the fresh Wordpress site should be available now this address: http://127.0.0.1:8000/

Progress:

• Prepare docker-compose.yml
• Add mysql service
• Add wordpress service
• Run the stack

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